Transmission having at least eight speeds

ABSTRACT

A transmission of the present invention has an input member, an output member, four planetary gear sets, a plurality of coupling members and a plurality of torque transmitting devices. Each of the planetary gear sets includes first, second and third members. The torque transmitting devices may include clutches and brakes. The torque transmitting devices are selectively engageable in combinations of at least three to establish at least eight forward speed ratios and at least one reverse speed ratio.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/614,128 filed on Nov. 6, 2009 and as such, claims priority theretounder 35 U.S.C. §120.

FIELD

The present invention relates generally to a multiple speed transmissionhaving a plurality of planetary gear sets and a plurality of torquetransmitting devices, and more particularly to a transmission havingeight or more speeds, four planetary gear sets and a plurality of torquetransmitting devices.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may or may not constitute priorart.

A typical multiple speed transmission uses a combination of frictionclutches and brakes, planetary gear arrangements and fixedinterconnections to achieve a plurality of gear ratios. The number andphysical arrangement of the planetary gear sets, generally, are dictatedby packaging, cost and desired speed ratios.

While current transmissions achieve their intended purpose, the need fornew and improved transmission configurations which exhibit improvedperformance, especially from the standpoints of efficiency,responsiveness and smoothness and improved packaging, primarily reducedsize and weight, is essentially constant. Accordingly, there is a needfor an improved, cost-effective, compact multiple speed transmission.

SUMMARY

A transmission is provided having an input member, an output member,four planetary gear sets, a plurality of coupling members and aplurality of torque transmitting devices. Each of the planetary gearsets includes first, second and third members. The torque transmittingdevices are for example clutches and brakes.

In an aspect of the present invention a transmission is provided havingan input member, an output member, a first, second, third and fourthplanetary gear sets each having sun gears, carrier members and ringgears. The input member is continuously interconnected with sun gearmember of the first planetary gear set. The output member iscontinuously interconnected with the ring gear member of the thirdplanetary gear set.

Additionally, a first interconnecting member continuously interconnectsthe carrier member of the first planetary gear set with ring gear memberof the second planetary gear set, a second interconnecting membercontinuously interconnects the ring gear member of the first planetarygear set with the carrier member of the fourth planetary gear set, athird interconnecting member continuously interconnects the carriermember of the second planetary gear set with the carrier member of thethird planetary gear set and a fourth interconnecting membercontinuously interconnects the sun gear member of the third planetarygear set with the ring gear member of the fourth planetary gear set.

Further, a first torque transmitting device is selectively engageable tointerconnect the carrier member of the first planetary gear set and thering gear member of the second planetary gear set with the ring gearmember of the fourth planetary gear set, a second torque transmittingdevice is selectively engageable to interconnect the input member andthe sun gear member of the first planetary gear set with the carriermember of the second planetary gear set, a third torque transmittingdevice is selectively engageable to interconnect the ring gear member ofthe first planetary gear set and the carrier member of the fourthplanetary gear set with the stationary member, a fourth torquetransmitting device is selectively engageable to interconnect the sungear member of the second planetary gear set with the stationary member,a fifth torque transmitting device is selectively engageable tointerconnect the carrier member of the second planetary gear set and thecarrier member of the third planetary gear set with the stationarymember and a sixth torque transmitting device selectively engageable tointerconnect the sun gear member of the fourth planetary gear set withthe stationary member. In operation, the torque transmitting devices areselectively engageable in combinations of at least three to establish atleast eight forward speed ratios and at least one reverse speed ratiobetween the input member and the output member.

It is thus an object, aspect and advantage of the present invention toprovide a transmission having four planetary gear sets.

It is a further object, aspect and advantage of the present invention toprovide a transmission having at least eight forward speeds and at leastone reverse.

It is a still further object, aspect and advantage of the presentinvention to provide a transmission having four planetary gear sets, aplurality of coupling members and a plurality of torque transmittingdevices.

Further objects, aspects and advantages of the present invention willbecome apparent by reference to the following description and appendeddrawings wherein like reference numbers refer to the same component,element or feature.

DRAWINGS

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

FIG. 1 is a lever diagram of an embodiment of a eight speed transmissionaccording to the present invention;

FIG. 2 is a diagrammatic view of an embodiment of a eight speedtransmission according to the present invention; and

FIG. 3 is a truth table presenting the state of engagement of thevarious torque transmitting elements in each of the available forwardand reverse speeds or gear ratios of the transmission illustrated inFIGS. 1 and 2.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses.

At the outset, it should be appreciated that in the particular exampleprovided, the eight speed automatic transmission of the presentinvention has an arrangement of permanent mechanical connections betweenthe components or elements of the four planetary gear sets. A secondcomponent or element of a first planetary gear set is permanentlycoupled to a third component or element of a second planetary gear set.A third component or element of the first planetary gear set ispermanently coupled to a second component or element of a fourthplanetary gear set. A second component or element of the secondplanetary gear set is permanently coupled to a second component orelement of a third planetary gear set. A first component or element ofthe third planetary gear set is permanently coupled to a third componentor element of a fourth planetary gear set.

Referring now to FIG. 1, an embodiment of an eight speed transmission 10is illustrated in a lever diagram format. A lever diagram is a schematicrepresentation of the components of a mechanical device such as anautomatic transmission. Each individual lever represents a planetarygear set wherein the three basic mechanical components of the planetarygear set are each represented by a node. Therefore, a single levercontains three nodes: one for the sun gear, one for the planet gearcarrier, and one for the ring gear. In some cases, two levers may becombined into a single lever having more than three nodes (typicallyfour nodes). For example, if two nodes on two different levers areinterconnected through a fixed connection they may be represented as asingle node on a single lever. The relative length between the nodes ofeach lever can be used to represent the ring-to-sun ratio of eachrespective gear set. These lever ratios, in turn, are used to vary thegear ratios of the transmission in order to achieve appropriate ratiosand ratio progression. Mechanical couplings or interconnections betweenthe nodes of the various planetary gear sets are illustrated by thin,horizontal lines and torque transmitting devices such as clutches andbrakes are presented as interleaved fingers. If the device is a brake,one set of the fingers is grounded. Further explanation of the format,purpose and use of lever diagrams can be found in SAE Paper 810102, “TheLever Analogy: A New Tool in Transmission Analysis” by Benford andLeising which is hereby fully incorporated by reference.

The transmission 10 includes an input shaft or member 12, a firstplanetary gear set 14, a second planetary gear set 16, a third planetarygear set 18, a fourth planetary gear set 20 and an output shaft ormember 22. In the lever diagram of FIG. 1, the first planetary gear set14 has three nodes each: a first node 14A, a second node 14B and a thirdnode 14C. The second planetary gear set 16 has three nodes each: a firstnode 16A, a second node 16B and a third node 16C. The third planetarygear set 18 has three nodes each: a first node 18A, a second node 18Band a third node 18C. The fourth planetary gear set 20 has three nodeseach: a first node 20A, a second node 20B and a third node 20C.

The input member 12 is coupled to the first node 14A of the firstplanetary gear set 14. The second node 14B of the first planetary gearset 14 is coupled to the third node 16C of the second planetary gear set16. The third node 14C of the first planetary gear set 14 is coupled tothe second node 20B of the fourth planetary gear set 20. The second node16B of the second planetary gear set 16 is coupled to the second node18B of the third planetary gear set 18. The first node 18A of the thirdplanetary gear set 18 is coupled to the third node 20C of the fourthplanetary gear set 20. The output member 22 is coupled to the third node18C of the third planetary gear set 18.

A first clutch 24 selectively connects the third node 16C of the secondplanetary gear set 16 and the second node 14B of the first planetarygear set 14 with the first node 18A of the third planetary gear set 18and the third node 20C of the fourth planetary gear set 20. A secondclutch 26 selectively connects the input member 12 and the first node14A of the first planetary gear set 14 with the second node 16B of thesecond planetary gear set 16 and the second node 18B of the thirdplanetary gear set 18. A first brake 28 selectively connects the thirdnode 14C of the first planetary gear set 14 and the second node 20B ofthe fourth planetary gear set 20 with a stationary element or atransmission housing 50. A second brake 30 selectively connects thefirst node 16A of the first planetary gear set 16 with the stationaryelement or a transmission housing 50. A third brake 32 selectivelyconnects the second node 16B of the second planetary gear set 16 and thesecond node 18B of the third planetary gear set 18 with a stationaryelement or a transmission housing 50. A fourth brake 34 selectivelyconnects the first node 20A of the fourth planetary gear set 20 with astationary element or a transmission housing 50.

Referring now to FIG. 2, a stick diagram presents a schematic layout ofthe embodiment of the eight speed transmission 10 according to thepresent invention. In FIG. 2, the numbering from the lever diagram ofFIG. 1 is carried over. The clutches, brakes, and couplings arecorrespondingly presented whereas the nodes of the planetary gear setsnow appear as components of planetary gear sets such as sun gears, ringgears, planet gears and planet gear carriers.

For example, the planetary gear set 14 includes a sun gear member 14A, aring gear member 14C and a planet gear carrier member 14B that rotatablysupports a set of planet gears 14D (only one of which is shown). Theplanet gears 14D are each configured to intermesh with both the sun gearmember 14A and the ring gear member 14C. The sun gear member 14A isconnected for common rotation with input shaft or member 12. The ringgear member 14C is connected for common rotation with a first shaft orinterconnecting member 42. The planet carrier member 14B is connectedfor common rotation with a second shaft or interconnecting member 44.

The planetary gear set 16 includes a sun gear member 16A, a ring gearmember 16C and a planet gear carrier member 16B that rotatably supportsa set of planet gears 16D (only one of which is shown). The planet gears16D are each configured to intermesh with both the sun gear member 16Aand the ring gear member 16C. The sun gear member 16A is connected forcommon rotation with a third shaft or interconnecting member 46. Thering gear member 16C is connected for common rotation with the secondshaft or interconnecting member 44. The planet carrier member 16B isconnected for common rotation with a fourth shaft or interconnectingmember 48 and a fifth shaft or interconnecting member 52.

The planetary gear set 18 includes a sun gear member 18A, a ring gearmember 18C and a planet gear carrier member 18B that rotatably supportsa set of planet gears 18D (only one of which is shown). The set ofplanet gears 18D are each configured to intermesh with both the sun gearmember 18A and the ring gear member 18C. The sun gear member 18A isconnected for common rotation with a sixth shaft or interconnectingmember 54. The ring gear member 18C is connected for common rotationwith the output shaft or member 22. The planet carrier member 18B isconnected for common rotation with a fifth shaft or interconnectingmember 52.

The planetary gear set 20 includes a sun gear member 20A, a ring gearmember 20C and a planet gear carrier member 20B that rotatably supportsa first set of planet gears 20D (only one of which is shown). The set ofplanet gears 20D are each configured to intermesh with both the sun gearmember 20A and the ring gear member 20C. The sun gear member 20A isconnected for common rotation with a seventh shaft or interconnectingmember 56. The ring gear member 20C is connected for common rotationwith the sixth shaft or interconnecting member 54 and with the eighthshaft or interconnecting member 58. The planet carrier member 20B isconnected for common rotation with the first shaft or interconnectingmember 42 and ninth shaft or interconnecting member 60.

The input shaft or member 12 is continuously connected to an engine (notshown) or to a turbine of a torque converter (not shown). The outputshaft or member 22 is continuously connected with the final drive unitor transfer case (not shown).

The torque-transmitting mechanisms or first clutch 24, second clutch 26and brakes 28, 30, 32 and 34 allow for selective interconnection of theshafts or interconnecting members, members of the planetary gear setsand the housing. For example, the first clutch 24 is selectivelyengageable to connect the second shaft or interconnecting member 44 withthe eighth shaft or interconnecting member 58. The second clutch 26 isselectively engageable to connect the input shaft or member 12 with thefourth shaft or interconnecting member 48. The first brake 28 isselectively engageable to connect the ninth shaft or interconnectingmember 60 with a stationary element or the transmission housing 50 inorder to prevent the ninth shaft or interconnecting member 60 fromrotating relative to the transmission housing 50. The second brake 30 isselectively engageable to connect the third shaft or interconnectingmember 46 with a stationary element or the transmission housing 50 inorder to prevent the third shaft or interconnecting member 46 fromrotating relative to the transmission housing 50. The third brake 32 isselectively engageable to connect the fifth shaft or interconnectingmember 52 with a stationary element or the transmission housing 50 inorder to prevent the fifth shaft or interconnecting member 52 fromrotating relative to the transmission housing 50. The fourth brake 34 isselectively engageable to connect the seventh shaft or interconnectingmember 56 with a stationary element or the transmission housing 50 inorder to prevent the seventh shaft or interconnecting member 56 fromrotating relative to the transmission housing 50.

Referring now to FIGS. 2 and 3, the operation of the embodiment of theeight speed transmission 10 will be described. It will be appreciatedthat the transmission 10 is capable of transmitting torque from theinput shaft or member 12 to the output shaft or member 22 in at leasteight forward speed or torque ratios and at least one reverse speed ortorque ratio with triple overdrive. Each forward and reverse speed ortorque ratio is attained by engagement of one or more of thetorque-transmitting mechanisms (i.e. first clutch 24, second clutch 26,first brake 28, second brake 30, third brake 32 and fourth brake 34), aswill be explained below. FIG. 3 is a truth table presenting the variouscombinations of torque-transmitting elements that are activated orengaged to achieve the various gear states. Actual numerical gear ratiosof the various gear states are also presented although it should beappreciated that these numerical values are exemplary only and that theymay be adjusted over significant ranges to accommodate variousapplications and operational criteria of the transmission 10. An exampleof the gear ratios that may be obtained using the embodiments of thepresent invention are also shown in FIG. 3. Of course, other gear ratiosare achievable depending on the gear diameter, gear teeth count and gearconfiguration selected.

To establish reverse gear, the first clutch 24, the third brake 32 andthe fourth brake 34 are engaged or activated. The first clutch 24connects the second shaft or interconnecting member 44 with the eighthshaft or interconnecting member 58. The third brake 32 connects thefifth shaft or interconnecting member 52 with a stationary element orthe transmission housing 50 in order to prevent the fifth shaft orinterconnecting member 52 from rotating relative to the transmissionhousing 50. The fourth brake 34 connects the seventh shaft orinterconnecting member 56 with a stationary element or the transmissionhousing 50 in order to prevent the seventh shaft or interconnectingmember 56 from rotating relative to the transmission housing 50.Likewise, the eight forward ratios are achieved through differentcombinations of clutch and brake engagement, as shown in FIG. 3.

It will be appreciated that the foregoing explanation of operation andgear states of the eight speed transmission 10 assumes, first of all,that all the clutches and brakes not specifically referenced in a givengear state are inactive or disengaged and, second of all, that duringgear shifts, i.e., changes of gear state, between at least adjacent gearstates, a clutch or brake engaged or activated in both gear states willremain engaged or activated.

The description of the invention is merely exemplary in nature andvariations that do not depart from the gist of the invention areintended to be within the scope of the invention. Such variations arenot to be regarded as a departure from the spirit and scope of theinvention.

What is claimed is:
 1. A transmission comprising: an input member; anoutput member; first, second, third and fourth planetary gear sets eachhaving first, second and third members; a plurality of interconnectingmembers each continuously interconnecting one of the first, second, andthird members of the planetary gear sets with another of the first,second, and third members of the planetary gear sets, wherein a first ofthe plurality of interconnecting members continuously interconnects thesecond member of the first planetary gear set with the third member ofthe second planetary gear set, a second of the plurality ofinterconnecting members continuously interconnects the third member ofthe first planetary gear set with the second member of the fourthplanetary gear set, and a third of the plurality of interconnectingmembers continuously interconnects the second member of the secondplanetary gear set with the second member of the third planetary gearset; a plurality of torque transmitting devices each selectivelyengageable to interconnect one of the first, second, and third membersof the planetary gear sets with another of the first, second, and thirdmembers of the planetary gear sets, or a stationary member, wherein fourof the plurality torque transmitting devices are brakes and two of theplurality torque transmitting devices are clutches, and wherein thetorque transmitting devices are selectively engageable in combinationsof at least three to establish a plurality of forward speed ratios andat least one reverse speed ratio between the input member and the outputmember.
 2. The transmission of claim 1 wherein a fourth of the pluralityof interconnecting members continuously interconnects the first memberof the third planetary gear set with the third member of the fourthplanetary gear set.
 3. The transmission of claim 1 wherein a first ofthe plurality of torque transmitting devices is selectively engageableto interconnect the second member of the first planetary gear set andthe third member of the second planetary gear set with the third memberof the fourth planetary gear set.
 4. The transmission of claim 3 whereina second of the plurality of torque transmitting devices is selectivelyengageable to interconnect the input member and the first member of thefirst planetary gear set with the second member of the second planetarygear set.
 5. The transmission of claim 4 wherein a third of theplurality of torque transmitting devices is selectively engageable tointerconnect the third member of the first planetary gear set and thesecond member of the fourth planetary gear set with the stationarymember.
 6. The transmission of claim 5 wherein a fourth of the pluralityof torque transmitting devices is selectively engageable to interconnectthe first member of the second planetary gear set with the stationarymember.
 7. The transmission of claim 6 wherein a fifth of the pluralityof torque transmitting devices is selectively engageable to interconnectthe second member of the second planetary gear set and the second memberof the third planetary gear set with the stationary member.
 8. Thetransmission of claim 7 wherein a sixth of the plurality of torquetransmitting devices is selectively engageable to interconnect the firstmember of the fourth planetary gear set with the stationary member. 9.The transmission of claim 1 wherein the first members of the planetarygear sets are sun gears, the second members of the planetary gear setsare carrier members, and the third members of the planetary gear setsare ring gears.
 10. The transmission of claim 1 wherein the input memberis continuously interconnected with the first member of the firstplanetary gear set and the output member is continuously interconnectedwith the third member of the third planetary gear set.
 11. Atransmission comprising: an input member; an output member; first,second, third and fourth planetary gear sets each having first, secondand third members, wherein the input member is continuouslyinterconnected with the first member of the first planetary gear set andthe output member is continuously interconnected with the third memberof the third planetary gear set; a plurality of interconnecting memberscontinuously interconnecting one of the first, second, and third membersof the planetary gear sets with another of the first, second, and thirdmembers of the planetary gear sets, wherein a first of the plurality ofinterconnecting members continuously interconnects the second member ofthe first planetary gear set with the third member of the secondplanetary gear set, a second of the plurality of interconnecting memberscontinuously interconnects the third member of the first planetary gearset with the second member of the fourth planetary gear set, and a thirdof the plurality of interconnecting members continuously interconnectsthe second member of the second planetary clear set with the secondmember of the third planetary gear set; a first torque transmittingdevice selectively engageable to interconnect the second member of thefirst planetary gear set and the third member of the second planetarygear set with the third member of the fourth planetary gear set; asecond torque transmitting device selectively engageable to interconnectthe input member and the first member of the first planetary gear setwith the second member of the second planetary gear set; a third torquetransmitting device selectively engageable to interconnect the thirdmember of the first planetary gear set and the second member of thefourth planetary gear set with a stationary member; a fourth torquetransmitting device selectively engageable to interconnect the firstmember of the second planetary gear set with the stationary member; afifth torque transmitting device selectively engageable to interconnectthe second member of the second planetary gear set and the second memberof the third planetary gear set with the stationary member; and a sixthtorque transmitting device selectively engageable to interconnect thefirst member of the fourth planetary gear set with the stationarymember, and wherein the torque transmitting devices are selectivelyengageable in combinations of at least three to establish at least eightforward speed ratios and at least one reverse speed ratio between theinput member and the output member.
 12. The transmission of claim 11wherein a fourth of the plurality of interconnecting memberscontinuously interconnects the first member of the third planetary gearset with the third member of the fourth planetary gear set.
 13. Thetransmission of claim 12 wherein the first members of the planetary gearsets are sun gears, the second members of the planetary gear sets arecarrier members, and the third members of the planetary gear sets arering gears.
 14. A transmission comprising: an input member; an outputmember; first, second, third and fourth planetary gear sets each havinga sun gear member, a carrier member and a ring gear member, wherein theinput member is continuously interconnected with the sun gear member ofthe first planetary gear set and the output member is continuouslyinterconnected with the ring gear member of the third planetary gearset; a plurality of interconnecting members each continuouslyinterconnecting one of the sun gears, carrier members, and ring gears ofthe planetary gear sets with another of the sun gears, carrier members,and ring gears of the planetary gear sets; a first torque transmittingdevice selectively engageable to interconnect the carrier member of thefirst planetary gear set and the ring gear member of the secondplanetary gear set with the ring gear member of the fourth planetarygear set; a second torque transmitting device selectively engageable tointerconnect the input member and the sun gear member of the firstplanetary gear set with the carrier member of the second planetary gearset; a third torque transmitting device selectively engageable tointerconnect the ring gear member of the first planetary gear set andthe carrier member of the fourth planetary gear set with a stationarymember; a fourth torque transmitting device selectively engageable tointerconnect the sun gear member of the second planetary gear set withthe stationary member; a fifth torque transmitting device selectivelyengageable to interconnect the carrier member of the second planetarygear set and the carrier member of the third planetary gear set with thestationary member; and a sixth torque transmitting device selectivelyengageable to interconnect the sun gear member of the fourth planetarygear set with the stationary member, and wherein the torque transmittingdevices are selectively engageable in combinations of at least three toestablish at least eight forward speed ratios and at least one reversespeed ratio between the input member and the output member.
 15. Thetransmission of claim 14 wherein a first of the plurality ofinterconnecting members continuously interconnects the carrier member ofthe first planetary gear set with the ring gear of the second planetarygear set.
 16. The transmission of claim 15 wherein a second of theplurality of interconnecting members continuously interconnects the ringgear of the first planetary gear set with the carrier member of thefourth planetary gear set.
 17. The transmission of claim 16 wherein athird of the plurality of interconnecting members continuouslyinterconnects the carrier member of the second planetary gear set withthe carrier member of the third planetary gear set.
 18. The transmissionof claim 17 wherein a fourth of the plurality of interconnecting memberscontinuously interconnects the sun gear of the third planetary gear setwith the ring gear of the fourth planetary gear set.